Actor Warren Beatty was on stage presenting the award with actress Faye Dunaway and he looked to Dunaway after hesitating to read the winner card.

Dunaway then announced that the award went to the musical "La La Land."

As the "La La Land" cast and crew was on stage giving acceptance speeches, "La La Land" producer Jordan Horowitz interrupted to say there had been a mistake and that coming-of-age drama "Moonlight" won Best Picture.

"This is not a joke," Horowitz said. "'Moonlight' has won Best Picture."

Accounting firm PricewaterhouseCoopers, which tallies Academy Awards votes, issued a statement apologizing to all involved and said that Dunaway and Beatty "had mistakenly been given the wrong category envelope and when discovered, was immediately corrected."

"We are currently investigating how this could have happened and deeply regret that this occurred," the firm said. "We appreciate the grace with which the nominees, the Academy, ABC and Jimmy Kimmel handled the situation."

"Moonlight" director Barry Jenkins and screenwriter Tarell Alvin McCraney reflected on the mistake on "CBS This Morning," with Jenkins saying the incident didn't necessarily diminish the win, but "made it much more complicated."

"it showed the camaraderie and love we have for both of the films," McCraney said.

We deeply regret the mistakes that were made during the presentation of the Best Picture category during last night’s Oscar ceremony. We apologize to the entire cast and crew of La La Land and Moonlight whose experience was profoundly altered by this error. We salute the tremendous grace they displayed under the circumstances. To all involved -- including our presenters Warren Beatty and Faye Dunaway, the filmmakers, and our fans watching worldwide -- we apologize.

For the last 83 years, the Academy has entrusted PwC to handle the critical tabulation process, including the accurate delivery of results. PwC has taken full responsibility for the breaches of established protocols that took place during the ceremony. We have spent last night and today investigating the circumstances, and will determine what actions are appropriate going forward. We are unwaveringly committed to upholding the integrity of the Oscars and the Academy of Motion Picture Arts and Sciences.